1. Field of the Invention
The present invention relates to an extendable antenna and a radio transceiver using the extendable antenna which comprises a first antenna portion and a second antenna portion provided at an end of the first antenna portion, a cylindrical antenna guide provided inside of a housing of the transceiver slidably retracting the first antenna portion, and a bottom hole for discharging water introduced into the antenna guide.
2. Description of the Related Art
FIGS. 10(a) and 10(b) show a prior art portable radio transceiver A having a circuit board C including a communication circuit (not shown) disposed within a housing B of the radio transceiver and, an extendable antenna D disposed in the housing B and extended along the circuit board C in the housing B.
The extendable antenna D includes an antenna member E which has a rod antenna portion Ea having a length of wavelength .lambda./4, for example, and a helical antenna portion Eb provided with a conductive portion having a length of wavelength .lambda./4 or .lambda./2 and connected to the tip end of the rod antenna portion Ea. The rod antenna portion Ea is provided at its base end (right end in the drawing) with a first contact portion Ec, while the helical antenna portion Eb is provided at its base end (right end in the drawing) with a second contact portion Ed.
Meanwhile, a cylindrical antenna guide F is disposed along the circuit board C in the interior of the housing B, and the rod antenna portion Ea of the antenna member E is slidably retracted into the antenna guide F formed by an insulating tube of smooth material such as Teflon (Trade Name of E. I. du Pont de Nemours & Co., Inc., U.S.A.).
That is, the antenna member E is mounted to be slidable to the housing B, so that, when the antenna member E is slid into the interior of the housing B, the rod antenna portion Ea is retracted within the housing B.
As shown in FIG. 10(b), when the rod antenna portion Ea of the antenna member E is extended from the housing B, the first contact portion Ec of the antenna member E fits in a power supply connection member G provided in the housing B.
As a result, electromagnetic waves received at the rod antenna portion Ea and helical antenna portion Eb are sent from the power supply connection member G through a contact terminal H contacted with the power supply connection member G to a receiver portion in the communication circuit of the circuit board C; whereas, a signal emitted from a transmitter portion of the communication circuit is sent to the rod antenna portion Ea and helical antenna portion Eb and transmitted therefrom.
When the rod antenna portion Ea of the antenna member E is retracted into the interior of the housing B so that only the helical antenna portion Eb is exposed to the outside of the housing B as shown in FIG. 10(a), on the other hand, the second contact portion Ed of the antenna member E fits in the power supply connection member G, whereby only the helical antenna portion Eb functions as the antenna.
Under such a condition as mentioned above, the first contact portion Ec of the antenna member E comes into contact with a contact terminal I which is grounded. Thus, the rod antenna portion Ea of the antenna member E does not function as the antenna.
With the radio transceiver A having the aforementioned arrangement, in the event where rain water is attached to the rod antenna portion Ea extended from the housing B as shown in FIG. 10(b), if the rod antenna portion Ea is retracted into the housing B without removing the rain water, there may occur a danger that the rain water is introduced from the rod antenna portion Ea along the antenna guide F into the housing B, which may undesirably result in that the communication circuit is disabled or broken when the rain water further intrudes into the communication circuit.
In order to beforehand prevent the intrusion of the rain water attached to the antenna member E into the interior of the housing B, it is considered to extend one end (right end in the drawing) of the antenna guide F up to a water drain hole Ba provided in the housing B. With this arrangement, however, when the rod antenna portion Ea of the antenna member E is retracted into the housing B, the first contact portion Ec of the antenna member E cannot be electrically connected to the contact terminal I. As a result, the rod antenna portion Ea of the antenna member E cannot be grounded and thus the function of the antenna member E may be deteriorated.